The Federal Communications Commission's own chief technology officer expressed concern Wednesday about Republican Chairman Ajit Pai's plan to repeal the net neutrality rules, saying it could lead to practices that are "not in the public interest."

In an internal email to all of the FCC commissioner offices, CTO Eric Burger, who was appointed by Pai in October, said the No. 1 issue with the repeal is concern that internet service providers will block or throttle specific websites, according to FCC sources who viewed the message.

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"Unfortunately, I realize we do not address that at all," Burger said in the email. "If the ISP is transparent about blocking legal content, there is nothing the [Federal Trade Commission] can do about it unless the FTC determines it was done for anti-competitive reasons. Allowing such blocking is not in the public interest."

The warning challenges the FCC's official line on the planned repeal of the net neutrality rules, set for a vote Thursday. While the agency is poised to scrap the rules preventing internet providers like Comcast and Verizon from blocking or throttling web traffic, the FCC's Republican majority argues consumers won't see a difference online.

An FCC official, speaking on the condition of anonymity to discuss the internal deliberations, said Burger's concerns have been addressed since his message Wednesday morning. The discussion, the official said, is part of the normal back-and-forth process of editing an FCC order.

The official said that some clarifying language was added to the order and that Burger replied Wednesday afternoon to say his concerns were "fully addressed." The official also noted that the CTO was focused on one section of the order and not the part that dealt with the rules.

Burger referred a request for comment to the FCC's media relations office.

Pai's planned repeal would scrap Obama-era rules preventing internet providers from blocking or throttling traffic, or negotiating paid deals with websites for faster access to consumers. In their place, providers must disclose their practices, with the FTC policing anti-competitive behavior.

Net neutrality advocates have been mounting a social media campaign to preserve the rules, and protesters have already begun to gather outside the FCC's headquarters in Washington ahead of Thursday's vote.